In 2016, Leist reunited with Double R Racing and graduated to BRDC British F3. Scoring four wins, two poles and six fastest laps, Leist took the title at the final round after a close fight with Ricky Collard throughout the season.[2]

In February 2017, Leist signed with Carlin for the Indy Lights Championship.[4] During his first season, Leist picked up his first podium at the Grand Prix of Indianapolis before taking pole and winning the Freedom 100 under two weeks later, having led from start to finish.[5]